The present invention relates generally to apparatus and methods for removing occluding materials from body lumens. More particularly, the present invention relates to the construction and use of atherectomy catheters for excising atheroma and other materials from blood vessels.
Cardiovascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the coronary and other vasculature, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous and other vascular deposits restrict blood flow and can cause ischemia which, in acute cases, can result in myocardial infarction. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque.
Atherosclerosis can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches which rely on intravascular widening or removal of the atheromatous or other material occluding a blood vessel. Of particular interest to the present invention, a variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to excise material from the blood vessel lumen generally employ a rotatable and/or axially translatable cutting blade which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. In particular, side-cutting atherectomy catheters generally employ a housing having an aperture on one side, a blade which is rotated or translated by the aperture, and a balloon or other deflecting structure to urge the aperture against the material to be removed.
Although atherectomy catheters have proven to be successful in treating many types of atherosclerosis, known catheter designs may be improved to further enhanced performance. For example, many known side-cutting atherectomy catheters have difficulty in capturing occluding material in the cutting aperture. Conventional atherectomy catheters typically use cutters mounted within openings on the sidewall of the catheter body. Some of these conventional catheters are difficult to position in the body lumen to engage the target tissue or material with these sidewall openings since the catheter must typically be positioned so that material will intrude into the opening. This may make it difficult to remove certain types of obstructions which do not lend themselves to being received in the catheter aperture. Furthermore, catheters which require material to intrude into the catheter aperture limit the aggressiveness with which materials can be removed in severe occlusion type blockages. Additionally, it is often difficult for conventional atherectomy cutters to apply the requisite pressure to cut off the targeted tissue or material. This decreases the effectiveness of these cutters and limits the cutter and catheter designs.
For these reasons, it is desired to provide atherectomy catheters which can access small, tortuous regions of the vasculature and which can remove atheromatous and other occluding materials from within blood vessels in a controlled fashion with minimum risk of injuring the blood vessel wall. In particular, it is desired to provide atherectomy catheters which can facilitate capturing and parting-off of occlusive material. It would also be particularly desirable to have catheters which can remove occlusive material located near the catheter but do not intrude into the catheter aperture. At least some of these objectives will be met by the catheter and method of the present invention described hereinafter and in the claims.
The present invention provides devices, methods, and kits for removing material from a body lumen. The catheters and methods of the present invention may be used in a variety of body lumens, including but not limited to coronary arteries and other blood vessels. In general, a catheter of the present invention has a scoop-shaped cutting blade mounted on a catheter body for removing material from a body lumen. The cutting blade has a cutting edge that travels a curved path about a pivot point of the blade, preferably moving in an outward direction from the catheter body to engage the target material for removal. The scoop-shaped blade has a collection surface located behind the cutting edge to collect material removed from said body lumen. Advantageously, a scoop-shaped cutting blade according to the present invention facilitates material engagement, and the collection surface may be used to bring material back into the catheter body as the blade begins to part-off material. The cutting blade is usually mounted to move in an inward direction towards the catheter body after the cutting edge has engaged the material. The scoop-shaped cutting blade can also more easily engage occlusive material that is compressed against the body lumen wall since the blade may be mounted to extend outward from the catheter body.
Desirably, the blade or blades of the catheter will be actuable with the application of reasonable mechanical forces which are capable of being transmitted along even rather lengthy catheters. Further desirably, the catheters will be suitable for directional removal of occluding material and will include mechanisms for engaging cutting blades against selected portions of a vascular wall. Optionally, the catheter should permit blood perfusion during performance of an atherectomy procedure. Preferably, but not necessarily, the cutting edge of the cutting blade will extend outside of the catheter body to engage material in a body lumen. Typically, the cutting blade rotates to place the cutting edge in the desired position. The arc defined by the rotation of the cutting blade is usually large enough to place the cutting edge outside the boundaries of the catheter body. The aperture from which the cutting blade extends may be located at a variety of positions on the catheter body, such as along the sidewall of the catheter or at the distal end of the catheter body. Devices having the cutting blade located at the distal end of the catheter may be used to bore through material in a substantially occluded body lumen. Preferably, the cutting blade has a mating surface on the catheter body to assist in the parting-off or cutting of material.
According to the present invention, embodiments of the catheter may have a scoop-shaped cutting blade that reciprocates longitudinally along a guide, such as a slotted track, a rail, or a ramp, to a position outside the catheter body. Furthermore, the cutting blade may be rotated about its pivot point while the blade is reciprocated longitudinally. A cutting blade that travels longitudinally while rotating about its pivot point can simulate the movement of a surgical curette/bone scraping device to remove greater amounts of material from the body lumen. Advantageously, such a rotating and translating motion may allow the catheter to lie stationary in the body lumen while the cutting blade travels out from the catheter body to grab material and return towards the catheter body to part it off. Rotation and translation also allows material to be removed and collected in a simultaneous manner. Rotation of the cutting blade may also increase the amount of force that may be applied against the material (since both translational and rotational force may be applied). The cutting blades used on the present invention may also include needles or other sharpened points to penetrate into the material to grasp the material before it is parted off.
In another aspect of the present invention, a method is provided for excising occlusive material from within a body lumen. The method comprises positioning a catheter body having a scoop-shaped cutting blade adjacent to a target material in the body lumen. Material may be parted off from the body lumen by rotating the cutting blade about a pivot point to engage and cut the target material while urging the material into the catheter body with a material collection surface on the cutting blade. Of course, in some embodiments, the cutting blade may translate longitudinally while being rotated about a pivot point of the cutting blade. The longitudinal moving step usually involves reciprocating the cutting blade between a first position where the cutting edge is outside the catheter body and a second position where the cutting edge is substantially within the catheter body.
In a still further aspect, kits according to the present invention will comprise a catheter having a material capture device. The kits will further include instructions for use setting forth a method as described above. Optionally, the kits will further include packaging suitable for containing the catheter and the instructions for use. Exemplary containers include pouches, trays, boxes, tubes, and the like. The instructions for use may be provided on a separate sheet of paper or other medium. Optionally, the instructions may be printed in whole or in part on the packaging. Usually, at least the catheter will be provided in a sterilized condition. Other kit components, such as a guidewire, may also be included.
A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.